1. Field of the Invention
The present invention relates to a method and apparatus for irradiating measuring light onto a solid-state image pickup device such as a CCD image sensor and a CMOS image sensor to inspect its electrical characteristics and in particular to an inspection method and inspection apparatus that allows downsizing of apparatus and high-speed inspection.
2. Description of the Related Art
When the electrical properties of a solid-state image pickup device, measuring light is irradiated onto the solid-state image pickup device. Related art inspection apparatus uses a halogen lamp as a light source and passes the light from the light source through a color filter to generate measuring light of a color necessary for measurement and through an ND filter to perform intensity adjustment of measuring light.
A halogen lamp has a short service life so that it must be changed frequently, which leads to higher costs. A mechanism for switching between color filters and introduction of an ND filter adds to the apparatus size. Further, filter switching at inspection takes time and a control signal is transmitted/received via GPIB (General Purpose Interface Bus: IEEE-488) communications thus resulting in lower control response.
JP-A-2-90645 discloses apparatus for inspecting a solid-state image pickup device using a light-emitting diode (LED) as a light source. By using an LED as a light source, the problems with the halogen lamp are solved.
While the color of the measuring light is not described in JP-A-2-90645, the technique described in JP-A-2004-213986, that is, the technique for controlling the value of a current applied to a red (R) LED, a green (G) LED and a blue (B) LED to perform color control of illumination light may be applied to apparatus for inspecting an solid-state image pickup device described in JP-A-2-90645 to do without a color filter. This downsizes the apparatus by the volume of the color filter and saves the time required for color filter switching during inspection.
The red LED, green LED and blue LED are respectively point light sources. Having certain sizes, the LEDs must be arranged in separate positions in the same inspection apparatus. It is thus necessary to provide a condensing optical system and light scattering means (obscure glass described in JP-A-2-90645) to keep uniform the additive color of light across the light receiving face of the solid-state image pickup device.
As mentioned above, a condensing optical system and light scattering means are required in inspection apparatus even when an LED is used as a light source for the inspection apparatus. Thus the inspection apparatus cannot be further downsized.